In recent years, a silicon photonics technique has been developed. This silicon photonics technique is a technique in which an optical device and an electronic device are connected by an optical circuit which uses optical waveguides made of silicon as a material. Thus, a semiconductor device in which an optical device and an electronic device are connected by using an optical circuit and on which these are mounted is referred to as a module for optical communication.
Of such semiconductor devices, there is a semiconductor device including optical waveguides composed of a semiconductor layer formed on abase substrate via an insulating layer as a transmission line for an optical signal and an insulating film formed to cover the optical waveguides. At this time, the optical waveguides serve as a core layer, and the insulating layer and the insulating film serve as cladding layers.
Japanese Patent Application Laid-Open Publication No. 2012-27198 (Patent Document 1) discloses an optical semiconductor device including a semiconductor layer which is an intrinsic semiconductor formed on a substrate, and optical waveguides which are parts of the semiconductor layer.